• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.291-294
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• 2000

The crystallization behavior and dc Conductivities of CuO-P$_2$O$_{5}$ -Nb$_2$O$_{5}$ -V$_2$O$_{5}$ glasses prepared by quenching on the copper plate were investigated. The conductivities of the glasses were range from 10$^{-5}$ s.$cm^{-1}$ / at room temperature, but the conductivities of the glass-ceramics were 10$^{-3}$ s.$cm^{-1}$ / increased by 10$^2$order. The crystalline product in the glass-ceramics was CuV$_2$O$_{6}$ . The linear relationship between in($\sigma$T) and T$^{-1}$ suggested that the electrical conduction in the present glass-ceramics would be due to a small polaron hopping mechanism.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.8
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• pp.617-621
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• 2010

($K_{0.5}Na_{0.5}$)($Nb_{0.96}Sb_{0.04}$)$O_3$+1.2 mol% $K_4CuNb_8O_{23}$ ceramics doped with iron oxide ($Fe_2O_3$) were prepared by a conventional mixed oxide method. And then, their piezoelectric and dielectric properties were investigated as a function of $Fe_2O_3$ addition. X-ray diffraction studies reveal that $Fe^{3+}$ diffuses into the NKN lattices to form a solid solution with a pure perovskite structure at room temperature. At the sintering temperature of $1,060^{\circ}C$, when 0.2 mol% $Fe_2O_3$ was doped, the piezoelectric constant ($d_{33}$), electromechanical coupling factor (Kp), and mechanical quality factor ($Q_m$) showed the excellent values of 131.67 pC/N, 0.436, and 696.36, respectively. Results show that $Fe_2O_3$ deped ($K_{0.5}Na_{0.5}$)($Nb_{0.96}Sb_{0.04}$)$O_3$+1.2 mol% $K_4CuNb_8O_{23}$ lead-free piezoelectric ceramics are a promising lead free material for piezoelectric transformer applications.

• The Korean Journal of Ceramics
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• v.6 no.2
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• pp.138-142
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• 2000

Thin film $LiNbO_3$MFS (metal-ferroelectric-semiconductor) capacitor showed improved characteristics such as low interface trap density, low interaction with Si substrate, and large remanent polarization. This paper reports ferroelectric $LiNbO_3$thin films grown directly on p-type Si (100) substrates by 13.56 MHz RF magnetron sputtering system for FRAM (ferroelectric random access memory) applications. RTA (rapid thermal anneal) treatment was performed for as-deposited films in an oxygen atmosphere at $600^{\circ}C$ for 60sec. We learned from X-ray diffraction that the RTA treated films were changed from amorphous to poly-crystalline $LiNbO_3$which exhibited (012), (015), (022), and (023) plane. Low temperature film growth and post RTA treatments improved the leakage current of $LiNbO_3$films while keeping other properties almost as same as high substrate temperature grown samples. The leakage current density of $LiNbO_3$films decreased from $10^{-5}$ to $10^{-7}$A/$\textrm{cm}^2$ after RTA treatment. Breakdown electric field of the films exhibited higher than 500 kV/cm. C-V curves showed the clockwise hysteresis which represents ferroelectric switching characteristics. Calculated dielectric constant of thin film $LiNbO_3$illustrated as high as 27.9. From ferroelectric measurement, the remanent polarization and coercive field were achieved as 1.37 $\muC/\textrm{cm}^2$ and 170 kV/cm, respectively.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.10
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• pp.77-84
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• 1997

The refractive index changes due to the electroptic effect are discussed when external electric fields $E_x, E_y, E_2$ are applied on $LiNbO_3$, a typical anisotropic material. Derived are approximate equations for principal axis' rotations and index changes, results of which are compared with exact results by te computer simulations. In each useful application of $LiNbO_3$substrate, the results of the approximate equations are confirmed to agree with exact solutions.

• Proceedings of the Materials Research Society of Korea Conference
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• 2000.11a
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• pp.77-77
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• 2000

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.7
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• pp.506-510
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• 2012

In this study, lead-free $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ ceramics were fabricated by conventional mixed oxide method. Structural and electrical properties of lead-free $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ ceramics with the variation of sintering temperature were investigated. As results of x-ray diffraction analysis, all specimens showed a typical polycrystalline perovskite structure without presence of the second phase. Sintered density increased with an increases of sintering temperature and the specimen sintered at $1,020^{\circ}C$ showed the maximum value of 4.5 $g/cm^3$. The average grain size of the $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ specimen sintered at $1,020^{\circ}C$ is about 0.83 ${\mu}m$. Electromechanical coupling factor, relative dielectric constant and dielectric loss of $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ specimens sintered at $1,020^{\circ}C$ were 0.252, 741 and 0.043% respectively.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1171-1172
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• 2006

Addition of 2.0wt%$Dy_2O_3$ or 0.3wt%Sn proved to be very effective in improving the permanent magnetic properties of NdFeNbB magnets. $Dy_2O_3$ additions result in the increase in the Hci and temperature dependence due to formation of (NdDy)-rich phase and grain refinement of $\Phi$ phase. This improvement of the coercivity stability of the magnets from the addition of Sn is attributed to the smoothing effect of the Sn addition at the grain boundaries. The magnetic properties, the temperature dependence and Curie temperature of NdFeNbB with $Dy_2O_3$ and Sn combined addition were found to be considerably improved.

• Bulletin of the Korean Chemical Society
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• v.17 no.8
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• pp.730-735
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• 1996

The layered perovskite oxide, KSr2Nb3O10, was synthesized. The interlayer potassium cations were readily exchanged by protons in hydrochloric acid solution to give the protonation compound, HSr2Nb3O10·0.5H2O. The intercalation compounds, [NH3(CH2)nNH3]xSr2Nb3O10, were also obtained by acid-base reactions between the protonation compound and organic bases, 1,n-alkyldiamines. The interlayer distances in the intercalation compounds were linearly increased with the increase of the number of carbon (Δc/Δn=1.05 Å) in 1,n-alkyldiamines. The intercalated alkyldiammonium ions formed a paraffin-like monolayer with average tilting angle (θ) of ca. 56°. The intercalation reactions occurred stoichiometrically. The thermal decomposition process of the intercalation compounds showed distinct three steps due to the desorption of hydrated water, the decomposition of organic moiety, and the decomposition of Sr-related compounds.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.139-142
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• 2003

Microwave dielectric properties of $Ca(Li_{1/4}Nb_{3/4})O_3-CaTiO_3$ ceramic systems were investigated with calcination temperatures and amounts of $CaTiO_3$ in the range of 0.2 to 0.4mol. $Ca(Li_{1/4}Nb_{3/4})O_3$ ceramics having orthorhombic crystal structure could be synthesized at $750^{\circ}C$ and sintered well at $1250^{\circ}C$. They showed the dielectric constant of 26, quality factor($Q{\times}f_o$) of 13,000 and temperature coefficient of resonant frequency(${\tau}_f$) of $-49{\pm}2ppm/^{\circ}C$ With adding the $CaTiO_3$ amount the dielectric constant and ${\tau}_f$ increased due to the solute of $CaTiO_3$ but the quality factor decreased. The 0.7$Ca(Li_{1/4}Nb_{3/4})O_3-0.3CaTiO_3$ ceramic showed the dielectric constant of 44, quality factor($Q{\times}f_o$) of 12,000 and ${\tau}_f$ of $-9{\pm}1ppm/^{\circ}C$.

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.160.2-160
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• 2002